The present invention relates to agricultural implements, and particularly to large agricultural implements adapted to be pulled behind modern tractors. As tractor horsepower has increased, so have the width of farm implements they pull to take advantage of the larger horsepower of such tractors. By way of example, the invention is illustrated and described as embodied in a row crop planter having twenty-four individual planter row units and which may extend sixty-five feet or more in the use position.
One important consideration of such large implements is the mode and manner in which they are transported to and from the field. Obviously, such an implement cannot be transported over roads in the same position or configuration in which it is set up for field use. Some early planters required separate trailers for transport. In addition to the cost for these special-use transport trailers, these planters are limited in length by the practical requirements of having to load the implement on the trailer and to unload it. In addition, valuable time is wasted in loading the implement on the trailer to transport it to a second field, and then in setting up the implement in the new field because the tractor must be unhitched from the implement and then hitched to the trailer and the reverse procedure followed at the new site. This time can be critical in view of the short time normally available when good planting conditions prevail, especially when numerous fields must be planted by the same implement.
Other attempts to facilitate transport of larger implements include frames with wings which fold vertically at the outer ends of the wings on which the row units are mounted. Vertically folding structures may be acceptable for cultivators and the like, but even here there is a limitation on the height of the implement for getting it under bridges, through gates and into sheds. In the case of a planter, however, vertically folding wings have the disadvantage that when the hoppers are turned on their sides, the lids may come loose during transport thereby spilling seed or insecticide. Other folding configurations include one which folds the outer portions of the mounting bar forwardly, leaving the center portion fixed. Here, there are limitations on the configurations of planting equipment that may be employed. Additional practical limitations are imposed on the length and width of these implements and there are disadvantages in converting them between use and transport configurations.
One improvement in planter design is disclosed in my U.S. Pat. No. 4,117,893. This system permits the planter bar to fold rearwarly about its centerline, and links are used to lock the two side sections or wings either in the use position in which the mounting bars are aligned and transverse to the direction of travel of the tractor. The same links lock the wings in the transport position, in which the mounting bars for the two sets of row units are folded rearwardly and are parallel to the direction of travel of the tractor. This system proved successful because it was capable of being converted between the use and transport position by a single operator in a matter of only seconds, and because it enabled planters of sixteen or eighteen or even twenty-four row configurations to be designed. Such larger planters are particularly desirable to operators of greater acreage where, as mentioned, the time during which ideal planting conditions exist may be short. A limitation on this system is the limited configurations of row units that may be employed. For instance, so-called interplant units cannot readily be employed because folding the planter already doubles the normal fore-to-aft length of the system which, during transport becomes the width of the system.
Another improvement in planter design is represented by the system disclosed in my U.S. Pat. No. 4,506,904. This system permits the planter bar to be transported endwise rather than by folding. One advantage of this system is that the tires are steered in the transport position to provide improved tracking of the large planter behind the tractor, even in sharp turns. The planter may be converted from planting configuration to transport configuration and back to planting configuration within minutes and without leaving the tractor seat.